Solid oxide fuel cell (SOFC) technology has been developed for application in transportation industry, primarily as an on-board auxiliary power unit (APU). Among others, the SOFC-based APU technology provides electric power for passenger cars, for instance for airco systems, lighting, electrically operating windows, breaking and steering systems, and the like.
SOFC-based APU systems can make use of a reformer system for fuelling the system once started. The reformer of choice up to now is a partial oxidation reformer (CPOx) that uses fuel and air, and catalytically converts it to primarily hydrogen, carbon monoxide, and nitrogen. It is housed inside the hot box and operates at high temperature. Such reformers are, for instance, disclosed in U.S. Pat. No. 5,968,680 and U.S. Pat. No. 6,562,496. The reformers according to the prior art are fed fuel and air through valves located in the main plenum chamber. The fuel is introduced through the insulated wall by way of an injector. The output from the CPOx mainly consisting of a carbon monoxide and hydrogen mixture is fed to the SOFC stack directly. This system has a few disadvantages, particularly the necessity to use heat exchangers, pre-heaters, and air blowers. These elements make the fuel system complicated and expensive. Further, according to U.S. Pat. No. 5,968,680 and U.S. Pat. No. 6,562,496 the CPOx mixes hydrocarboneous fuel with heated air to combust or oxidize the mixture. Such a reformer allows a single fuel delivery to the SOFC, but develops very high temperatures in the reformer, leading to accelerated catalyst degradation and coke deposition.
For that reason there is a need for a method for using such units, which is devoid of these disadvantages.
It has now been found that these problems can be solved when the exhaust gas of an internal combustion engine is used to replace at least part of the oxygen to be fed to the partial oxidation reformer.